This invention pertains to an improved ambulatory blood pump, which means a blood pump carried by a freely moving patient, either internally (implanted) or outside the body. It may take any form including left ventricular assist device, bi-ventricular assist device, right ventricular assist device, or total artificial heart.
Patients who have experienced severe heart failure are often considered candidates for heart transplantation. However, the number of people who need a heart transplant far exceeds the number of donor hearts available. As a result, mechanical blood pumps are used to sustain patients until a donor heart is available (e.g. xe2x80x9cbridge to transplantxe2x80x9d). Ultimately the clinical goal is to develop a blood pump small enough and reliable enough to serve as a chronic organ replacement for patients with heart failure, obviating the need for heart transplants in many cases.
Currently available blood pumps use mechanical mechanisms to move the patient""s blood. Typical technologies include pusher-plate (for example U.S. Pat. No. 5,511,958), centrifugal (for example U.S. Pat No. 5,803,720), and turbine or axial flow (for example U.S. Pat. No. 4,908,012). As described in U.S. Pat. No. 5,678,306 a major concern is damage to the blood cells from the pump. Smoll (U.S. Pat. No. 5,685,698) suggests the use of the Lorentz force to propel the blood with a pump having no moving parts. As he notes, similar technology has been applied to the propulsion of marine vessels as exemplified in U.S. Pat. No. 5,668,420. However, the efficiency of a pump using the Lorentz force is lower than mechanical pumps. Furthermore, in the Smoll patent the electrodes are not in direct blood contact, further impairing the transfer of electrical energy to blood motion.
Currently available ambulatory blood pumps often use a combination of an implanted battery and an external battery pack. The patient has to recharge the batteries frequently to keep the pump working. Furthermore, the external batteries are heavy, and are a significant burden to a patient with compromised cardiac function. To overcome the lower efficiency of a blood pump using the Lorentz force, and to provide the patient with a more easily portable power supply, the subject invention employs fuel cells as a means of storing energy.
Therefore it is a purpose of this invention to provide an improved ambulatory blood pump having no moving parts; and it is a further a purpose of this invention to provide an improved power source for ambulatory blood pumps.
This patent describes an improved ambulatory blood pump. The pump has no moving parts and operates by the application of the Lorentz force on the blood. Electrodes in direct blood contact are employed to improve electrical energy transfer to blood motion. High surface area electrodes, electrode coatings, electrode shape and time varying electrical and magnetic fields are used to diminish the effects of electolysis that would otherwise generate gas bubbles. It is recognized that the electrical efficiency of a pump using the Lorentz force is lower than a mechanical pump, and a novel energy source employing fuel cells is used to overcome the deficiency. The same energy source can also be used advantageously to reduce the weight of conventional ambulatory blood pumps.
A first object of the invention is a blood pump comprising a magnetic field and an electric field whereby blood is pumped by a Lorentz force. A second object of the invention is a blood pump wherein the electrodes have an enhanced surface area for the reduction of gas evolution at the electrode surface area. A third object of the invention is a blood pump were the polarity of the voltage applied to the electrodes and the polarity of the magnetic field are reversed to reduce gas evolution from the elecrodes. A fourth object of the invention is a blood pump powered by fuel cells. A fifth object of the invention is a blood pump having a fuel cell which has charge provided non-invasively through a biological barrier such as living tissue.